The layered structures with flexible circuit film are generally used in the actuation structure of keyswitch. The conventional keyswitch comprises layered structure including a lower flex circuit board, an upper flex circuit board and a spacer layer. The lower flex circuit board has a plurality of electric contacts on the upper surface thereof. The upper flex circuit board is arranged upon the lower flex circuit board and has a plurality of electric contacts on the bottom side thereof and corresponding to the contacts of the lower layer. The spacer layer is sandwiched between the upper and the lower layers and has a plurality of through holes corresponding to those contacts. When the key cap is pressed, the rubber dome below the key cap is collapsed such that the contacts on the upper and the lower layers are electrically connected. When the key cap is released, the contacts on the upper and lower layers are separated due to the elastically restoring force of the rubber dome.
However, the upper and lower circuit layer, and the spacer layer in the conventional switch are tightly attached together, a closed space is easily formed within each through hole. A nearly vacuum state is established in the through hole when the key cap is pressed and air is repelled from the through hole. The upper layer is hard to separate from the lower layer quickly and the electrical connection state is remained due to the sucking force of the nearly vacuum state. Therefore, letter or command input by the keyswitch will be probably repeated.
Therefore, there is an endeavor in preventing the sucking effect. As shown in FIGS. 1A and 1B, at least one first spacer block 11 is arranged around the contact 10 of the upper layer circuit 1, and at least one second spacer block 21 is arranged around the contact 20 of the lower layer 2 and corresponding to the first block 11. The distance between the two blocks 11 and 21 is smaller than the distance between the two contacts 10 and 20 such that the two blocks will be in contact before the connection of the two contact when key is pressed. Therefore, an air leaking passage is provided. However, in above configuration, both the first block 11 and the second block 21 are formed within the round hole 30 on the spacer 3. In other word, the upper layer 1, lower layer 2 and the spacer 3 outside the hole 30 are still tightly closed even after the key cap is released. The air passages 31 provided by the blocks 11 and 21 do not function well because they are placed within the closed space 30. The vacuum sucking effect still remains.
FIGS. 2A and 2B show another conventional keyswitch wherein the first block 11 around the contact 10 of the upper layer 1 and the second block 21 around the contact 20 of the lower 2 are in contact before the key be pressed. Moreover, the two contacts are separated by a specific distance before key pressing and in contact after key pressing, thus provides air outlet. However, the blocks 11 and 21 are of ring-shaped configuration around the corresponding contacts and have long distance to the contacts such that the upper layer 1 may fall on the lower layer 2 due to the weight themselves. A closed ring is formed around the first block 11 and the second block. Therefore, the vacuum sucking effect still remains.
It is an object of the present invention to provide a layered structure for keyswitch wherein a plurality of projecting flanges are arranged radially outside the through holes of the spacer layer, and placed on the lower surface of the upper layer, the upper surface of the lower layer or the spacer. The flanges separate the spacer and the flex circuit layer such that air leaking passage is formed between two adjacent flanges and the vacuum sucking effect is substantially prevented.
It is another object of the present invention to provide a layered structure for keyswitch wherein a plurality of projecting flanges are provided radially on the upper or lower surface of the spacer layer, the lower surface of the upper layer or the upper surface of the lower layer, and arranged in a broad region and with uniform separation. The layer can sustain more pressure and the air can flow uniformly and smoothly within the keyswitch.